No. We’re encouraged not to use the std library. Here’s a related link that might help: How to use C++ Standard Library? (std) - Programming & Scripting - Epic Developer Community Forums
String related classes:
FString: FString | Unreal Engine Documentation
FText: FText | Unreal Engine Documentation
FName: FName | Unreal Engine Documentation
Implementing your own, and narrowing its use to strings makes it easier, seems like your best choice.